1. Field of the Invention
The present invention relates to CMOS clearing circuits, particularly to a CMOS clearing circuit capable of choosing clearing method.
2. Description of Related Art
CMOS is a readable and writable memory integrated in a south bridge chip mounted on a computer motherboard, which is made of complementary metal oxide semiconductor, for storing hardware configuration of a current computer system and parameters set by users. CMOS parameters are often set by a CMOS setting program in a BIOS (Basic Input & Output System) chip. After CMOS parameters are set, the parameters are stored in the south bridge chip. Once the computer is restarted, the parameters will be adopted in the POST (Power On Self Test) process for changing hardware configuration. Users can enter the CMOS setting program in BIOS via pressing a specific key of the computer to set CMOS parameters as soon as the computer is started. The CMOS data stored in the south bridge chip is changed after setting the parameters. However, the computer may not be able to work normally if the CMOS parameters are set wrong, and users cannot enter computer system to amend CMOS data again. At this time, a method for rescuing the computer is to clear CMOS data stored in the south bridge chip. Conventionally, one CMOS clearing method is to directly clear CMOS data in the south bridge chip via hardware. Another CMOS clearing method is to clear CMOS data via BIOS when the computer is started. Generally, only one method is used in the computer motherboard. However, in actual use, different users may need different CMOS clearing methods. The motherboard that only uses one CMOS clearing method cannot meet different requirements of different customers.
What is needed, therefore, is a CMOS clearing circuit capable of applying different CMOS clearing methods to satisfy different customer requirements.